Method for the designing of tools

ABSTRACT

The invention concerns a method for the creation of addendums ( 4 ) of tools for sheet metal formed parts ( 2 ). In the case of this method, fill surfaces ( 7 ) for the smoothing of irregular zones of a component edge ( 3 ) are generated. Initial directions ( 31 ) of sectional profiles ( 10 ) are determined in such a manner, that sectional profiles ( 10 ) at a distance from one another are arranged along a component ( 3, 8 ) with utilization of these initial directions ( 31 ) and that an addendum ( 4 ) is creatable by the connection of these sectional profiles ( 10 ).

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending application Ser. No.10/275,633, filed on 21 Apr. 2003. The co-pending parent application ishereby incorporated by reference herein and is made a part hereof,including but not limited to those portions which specifically appearhereinafter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention presented here lies in the field of the designing ofaddendum zones of tools for the manufacture of formed sheet metal parts(deep-drawing/stretch-forming processes) and their optimization.

2. Discussion of Related Art

Formed sheet metal parts as a rule are manufactured by deep-drawing. Thesemi-finished parts, the so-called sheet metal blanks (blank), for thispurpose are placed in multi-part forming tools. By means of presses, inwhich the forming tools are clamped, the parts are formed. The parts, asa rule, are manufactured out of a flat sheet metal blank in severalforming steps (drawing, reshaping, setting, etc.), combined withtrimming steps. In this process the edge areas, in particular theaddendums, represent problematic zones. In the designing of the toolsfor a forming step the concern is, among others, to complement thecorrespondingly prepared component geometry. In the case of multi-stepprocesses, intermediate geometry (component geometry and intermediategeometry both being hereinafter referred to as component geometry) inthe edge zones is modified by an addendum such that, from it, a toolgeometry is produced with which the predefined component geometry can bemanufactured such that no failure occurs (cracks and wrinkles) and thatother quality requirements, for example, a limited reduction of thethickness, the achievement of a minimum stretching of the sheet metal,and manufacturing technology restrictions are adhered to.

The dimensioning and adjustment of the addendums represents a greatproblem field today. Not infrequently several months elapse, until atool works satisfactorily. Frequently, this is an iterative process,which is associated with a lot of rejected parts and a substantialconsumption of energy and other utilities. The production of addendumstoday, to a great extent, takes place manually by means ofcomputer-aided design systems (CAD) and takes a lot of time. In doingso, frequently hundreds of individual surfaces are created and edited bythe designing of curves, supporting surfaces derived from them, andtheir trimming. Already solely the establishment of an addendum for alarge body part can, as a result, easily take several weeks. Thisprocedure also calls for a great specialist knowledge in the fields offorming technology and CAD of the designer.

In the recent past, procedures have been developed and implemented,which make possible the creation of addendums in a more efficientmanner. These are based on an addendum being described by means of flatsectional profiles. The known sectional profiles are different to link,resulting in bad interpolation data for addendum surfaces. For mosttools, in addition, a limited number of such sectional profile types aresufficient. If one applies sufficient flat sectional profiles radiallyoutwards from the component edge, then from it, by an interpolationtransverse to the sectional profiles, the addendum surface can be moreor less automatically created. In doing so, the indication of a fewsectional profiles is sufficient to be able to then interpolate thesectional profiles from it. This method is not convincing. By avariation of the sectional profiles the addendum can be varied. Withthis procedure, the user, as compared to previous iterative methods, cansave time in the development and modification of the addendum. Theresulting addendum surfaces are still problematic due to insufficientresults from interpolation. These procedures are stand alone solutionsnot linked with other devices, e.g. simulation modules.

This procedure, however, has the following serious disadvantages andproblems. On the one hand, the smoothing of the edge of the componentrepresents a major problem. The edge of the component geometry, wherethe addendum is to be applied, is in most instances not a smooth curve,but rather more frequently has sharp-angled indentations, tongues, etc.If now the same sectional profile throughout is applied to this edge,then these indentations, etc. continue into the addendum, which can leadto an extremely irregular addendum surface. In order to prevent this,the user once again is compelled to manually introduce many sectionalprofiles at the indentations and to adapt them such that they lead to afairly smooth addendum surface. Alternatively, it is attempted to firstfill up and to equalize the indentations, tongues, etc., with the helpof traditional CAD functionality, so that a new, sufficiently largesmooth component edge is produced, from which then the sectionalprofiles are applied. Both solutions require a lot of time and lead tothe result that no usable addendum can be produced fully automatically.The latter fact is a disadvantage, particularly if one would like toautomatically design, resp., optimize the addendum via an optimizationloop in conjunction with a forming simulation code and a qualitycriterion. On the other hand, the sectional profile direction isdifficult to determine automatically. The directions in which thesectional profiles are applied away from the component edge (resp., fromthe filled out component edge), decisively determine the generatedaddendum surfaces. In applying the directions vertical to the edge ofthe component projected in the drawing direction, at concave pointsoverlaps of the sectional profiles result, which makes the creation ofthe addendum surface impossible.

SUMMARY OF THE INVENTION

It is an objective of the present invention to demonstrate a method howaddendum surfaces for forming tools can be optimized and createdefficiently and easily while avoiding the disadvantages known from priorart.

The invention divulged here is embedded in the process of tool designing(methods planning). The invention makes possible a significant reductionof the manufacturing effort, in that a new computer-based methodology isapplied. Apart from the possibility of creating and varying an addendumsignificantly more rapidly, in doing so it is also possible to create abest possible tool via an optimization loop in conjunction with aforming simulation code. The procedure described in the presentinvention for the establishment of a parameterized geometry and processmodel, starting out from the component geometry, can be summarized in asimplified manner with the following steps. First, prepare the componentgeometry; second, determine the direction of drawing; third, createsurface for the smoothing of irregular zones of the edge of thecomponent; fourth, generate binder surface; fifth, determine sectionalprofile directions; sixth, definition of sectional profiles at definedpoints; seventh, interpolation of intermediate profiles using formingtechnology parameters for the creation of the addendum surfaces; eighth,interactively adapt the characteristic lines, resp., automaticallysmooth them and correspondingly adapt addendum surfaces; ninth, creationof the punch opening line as intersections of the sectional profileswith a binder surface and the smoothing, resp., modification of it. Whentaking over the tool model into the simulation, the following steps forthe definition of the process models follow: Extraction of theindividual tool components from the generated geometries; specificationof the blank outline or, in the case of inverse simulation procedures,of the outline of the drawn-in sheet metal; specification of thematerial, of the sheet metal thickness and of the direction of rolling;specification of the lubrication conditions; definition of the retainingdevices (for example, draw bead, spacer, binder force); determination ofthe tool movements and of possible relieving steps during the forming.Iterative procedure between several of the above mentioned steps havingan alternative sequence is likely if necessary. And single steps mayalso be omitted.

A tool for the forming of a blank in one stage as a rule consists ofthree parts: A die, a binder, and a punch. By means of the binder, whichusually has a curved shape, the blank is pre-formed and fixed in an edgezone of the die. The actual deep drawing takes place, in that the blankis pressed into the die by means of the punch. The edge zones areusually designated as complementary surfaces. These then are dividedinto binder surfaces located outside the punch zone and the addendumlocated inside the punch. These zones are decisive to fulfil the qualityrequirements. The addendum as a rule runs into the component and thebinder with a continuous tangent and is located within the action zoneof the die and of the punch. In the case of components with largecut-outs, such as the side wall frames of passenger vehicles, inaddition to the external addendum several additional internal addendumscan be present.

The invention presented here concerns a method, which makes it possible,starting out from the geometry of a component, to as rapidly as possibleestablish a parameterized addendum and, if so required, a parameterizedgeometry and process model for a forming simulation based thereon. Theobjective is, as early as possible during development, possibly alreadyduring the design of the component, to make statements about the formingand manufacturing feasibility of a component with the help of formingsimulations and taking into account addendums. With this, it is possibleto make required corrections to the geometry of the component at anearly point in time. By means of a suitable parameterization it ispossible that the tool geometry (as well as the addendum) and theprocess can be varied by means of few, scalar parameters. For a rapidassessment of different variants or also with a view to the automaticcreation of an optimal addendum, if so required an optimization loopand/or a forming simulation code and/or a quality criterion are utilizedin combination.

For the following description of the invention the assumption isdeparted from, that the forming tools move in a global z-coordinatedirection. This direction is designated as vertical; directions verticalto this axis (x, y-directions) are designated as horizontal. Forpurposes of simplification, it is assumed that a component is free ofundercuts, i.e., the projection in z-direction onto a horizontal planeshall be a one-to-one correspondence, with the exception of componentsurfaces in an exactly vertical direction.

The present invention also pertains to smoothing irregular zones of thecomponent edges automatically or manually, in preference towards theoutside, i.e., away from the problem zones, and to automatically fill upthe space produced with optimized fill surfaces. These smoothed edges ofthe component are hereinafter referred to as base lines. They can eitherbe manually predefined or, for example, generated by geometricalsmoothing algorithms, for example, by the virtual “unrolling” of acylinder with a vertical axis along the edge of the component; thisdefines the x- and y-coordinate of the base line; the z-coordinate isadvantageously generated by the creation of the fill surfaces. Fillsurfaces making sense preferably run into the component geometry with acontinuous tangent. Such surfaces are, for example, generated by meansof geometrical approximations taking into consideration the C1 edgecondition (at the component edge), or, for example, by means of a finiteelements shell solution with corresponding edge condition at the edge ofthe component (in this context refer to FIG. 2).

The horizontal directions of the sectional profiles as a rule determinehow a geometrical detail of the component (feature), which extends tothe edge of the component, affects the addendum. It is, therefore,advantageous that geometrical details in the component geometry andtheir branches in the addendum essentially have the same direction. Thispresupposes, that a certain direction of the sectional profiles is aprerequisite (in this context refer to FIGS. 10, 11, 12).

In the present invention, the initial directions of the sectionalprofiles on the edge of a component are preferably determined such thatthey point in the direction of the minimum geometrical change in adefined, fictitious edge zone of the component or in correlation withthe flow-direction of the material. Alternative arrangements, such as inconcave areas, are possible to avoid negative overlapping. Thefictitious edge zone of the component is here notionally formed by afictitious strip along the edge of the component (resp., the base line),lying in the inside of the component. This edge zone as a rule has awidth, which is, for example, approximately 10-times the thickness ofthe sheet metal. How the direction of the minimum geometry change can bedetermined is illustrated in FIG. 5. If necessary, adjustments of theinitial directions are possible to avoid disadvantageous overlapping ofsectional profiles in concave areas.

In order to avoid the problem field associated with prior art of anoverlapping of sectional profiles, in particular in the zone of concaveedge points of a component, the invention makes use of defined sectionalprofiles. These as a rule do not run in a plane, but in a curvedsurface. Alternative arrangements are possible as long as nointersection is occurring. Preferred examples of such surfaces arecylindrical or parabolic surfaces with a vertical alignment. Thesectional curves of these profiles with a horizontal plane are thereforecurved or straight curves. These curves serve as horizontal directrixesfor the sectional profile. The course of the directrixes is determinedby means of geometrical algorithms (polynomial approaches).Alternatively, it is also possible to proceed as follows: Departing fromthe edge of the component, the curves are applied as flectional beams,which are fixed to the edge of the component in the direction of aminimum geometry change and are connected transverse to one another withan elastic continuum or with springs. A corresponding model, forexample, is brought to the static equilibrium with the finite elementsmethod (FEM). (In this context refer to FIG. 4).

According to prior art, up until now the vertical course of thesectional profiles was predefined either through spline curves (forexample, B-splines or Bézier curves) or through geometrical basicelements such as line segments, curves, etc, which are put together in atangent-continuous course. While the first makes possible an easychanging of a sectional profile, it has, however, the disadvantage thataccurate dimensions or the accurate geometry of a part of a curve, forexample, a draw bar height or a draw bar radius, it is very difficult toaccurately predefine. In the case of the second type of specification,while accurate dimensions can be determined, changes, however, arelaborious, because the tangent condition between the basic elementsalways has to be adhered to. In order to create addendum surfaces, inaddition the not-predefined sectional profiles (intermediate profiles)had to be generated from the closest predefined sectional profiles. Ifthese predefined sectional profiles deviated strongly from one another,an automatic interpolation in general led to insufficiently flatsurfaces, resp., to unexpected and undesirable intermediate forms. Forexample, a large circular arc predefined within a sectional profilewould not necessarily be continuously transformed into a smallerpredefined circular arc in the next sectional profile through circulararcs with reducing radii, but, depending on the interpolation, throughnon-circular intermediate forms. This problem was partially overcome, ifthe user accepted, that between the differing sectional profile typesmanual transition elements (junctions) have to be defined.

The problem field described above is solved preferably as follows in thecase of the invention divulged here: The sectional profiles arepreferably described by a single type of geometry, (see FIG. 9), whichhas to be sufficiently general in nature to be able to describe thecommon sectional profile forms. Sectional profiles arranged next to eachother are of corresponding nature making sure that no interpolationerrors occur. These sectional profiles are parameterized by formingtechnology scalar values easy to comprehend by the user (hereinafterreferred to as profile parameters), such as, for example, componentrun-off length, flange length, flange angle, draw bar height, draw barwidth, draw bar radius, step height, wall angle, die radius, etc. Thesectional profile is then built up based on these profile parameters outof basic elements, for example, circular arcs and line segments, in anautomated manner (in this context refer to FIG. 9). In the case ofinconsistent profile parameters, these are automatically adapted andoptimized in accordance with a defined priority. In this manner, asectional profile can be predefined exceedingly easily and clearly.

The courses of the intermediate profiles lying between the definedsectional profiles, in contrast to prior art, are, as a rule, notdirectly interpolated. Rather, first the profile parameters for everyintermediate profile relevant to forming technology are established.From these (interpolated) values then the course of the intermediateprofiles is built up. This, in the case of the example mentioned above,leads to the consequence that the predefined large circular arc istransformed into the predefined small circular arc through exactcircular arcs with reducing radii, if the corresponding radius is such aprofile parameter.

In the case of the methods for the creation of addendums known fromprior art, height differences and tangent jumps along the edge of thecomponent have an effect up to the punch opening line. This in generalis undesirable. With the methods known from prior art it is, therefore,necessary to correct these jumps manually by means of laborious andtime-intensive adaptation of the sectional profiles. Here too,automation is practically impossible.

In the case of the invention divulged here, this problem is solved asfollows. Sectional profiles possess characteristic points, whichdescribe the principal course of the sectional profile, Mentioned asexamples for such characteristic points shall be a summit of a draw bar,the flank of a step or the control points of a spline, of a Bézier- orof a NURBS curve. Those characteristic points of every sectional profilecorresponding to one another can now be joined together and with thisform (continuous) characteristic lines, which extend along an addendum(parallel to a component edge) or at least over sections of it, e.g.,the summit line of a draw bar (refer to FIG. 7). The lines defined inthis manner are especially suitable for changing the addenduminteractively, in that they, for example, are approximated as splineseasily variable through control points. Both changes in a verticaldirection (i.e., for example, the course of the height of a draw bar) aswell as changes in horizontal direction (i.e., for example thehorizontal position of the draw bar) can be implemented with this. Thechange specifically influences the corresponding parameters of thesectional profiles lying in the area of the change and correspondinglythe addendum surface. Since a change of a characteristic line in acontrolled manner influences several adjacent sectional profiles, such achange is significantly easier to implement than by means of the(manual) changing of individual sectional profiles. If the changing of aprofile parameter is to lead to changes of other profile parameters inthe adjacent sections (e.g., the changing of the draw bar height shallsimultaneously cause a change of the width of the draw bar), then acorresponding working connection can be defined by a coupling matrix. Inthe case of the method described here, it is also possible toautomatically smooth the characteristic lines. With this, geometry jumpsat the edge of the component can be easily smoothed (in this contextrefer to FIG. 18). As smoothing algorithms, for example, one can againutilize uncoiling algorithms, and this both in the horizontal plane aswell as in the height.

The concept of the characteristic lines can also be transferred toprofile parameters, which cannot be represented as a spatial line on theaddendum, e.g., the run-in radius or a draw bar radius. Such profileparameters are advantageously represented as characteristic lines in anx-y diagram, whereby on the abscissa the path around the addendum and onthe ordinate the profile parameter is applied. The resulting curve can,for example, once again be approximated as a spline easily variablethrough control points. Interactive or automatic changes (e.g.,smoothing) are transformed into a change of the addendum surface inanalogy to the procedure described in the preceding paragraph. Thisprocedure, of course, is also alternatively applicable to the profileparameters that can be represented as a spatial line.

If the generated tool geometry is to be checked by means of a formingsimulation, or if it is to be automatically optimized in an optimizationloop together with a forming simulation code and a quality criterion,then now still lacking is the tying into the forming simulation. For theforming simulation, as a rule three methods are utilized.

Single-step/multi-step simulations based on the component geometry.These are usually carried out in accordance with an inverse process,whereby the component geometry is departed from, it is squashed flat andthe resulting elongations in the flat sheet metal are, in principle,depicted inverted on the component. As a result of the neglecting of theimportant influence of the addendum and of the binder, such simulationsrepresent a rough estimate. Here they are irrelevant, because theconcern here is the assessment of a tool design.

Single-step/multi-step simulations based on the tool geometry: Usuallycarried out in accordance with the same method, here the geometry of theaddendum and of the binder as well as the retaining devices (e.g., drawbeads, binder force) are taken into consideration in the binder.Required as geometry here is that of the complete tool, therefore, inprinciple the die. The resulting accuracy enables the assessment of atool design, however, no direct statements about the behaviour of thesheet metal during the forming can be made. An important result of aninverse single step simulation is the required outline of the blank,which is required in order to achieve the outline of the predefinedgeometry at the end of the drawing process. Single-step/multi-stepsimulations can also be carried out as forwards method, i.e., departingfrom the blank.

Incremental simulations based on the tool geometry: Here, departing fromthe flat blank the forming is simulated in time steps (incrementally).The essential geometrical and process-conditioned influencing values canbe jointly taken into consideration accurately. A geometricaldescription of all participating tools is required, therefore, for thesimplest forming process a die, a punch, and a binder. This method isthe most accurate simulation method, calls for, however, significantlymore calculation time than a single step process. Available as theresult apart from the end condition are also the intermediateconditions.

For the checking of a tool geometry, the two latter methods arepossible. Current systems for the generation of tools are, however, notvery closely linked to forming simulation systems, so that for theimplementation of simulations in most instances a considerable effortthrough various interfaces and data conversions has to be undertaken.

The method described above for the creation of addendum zones,preferably is combinable with a system in which a parameterizedsimulation model (tool or process) is utilized for the optimization of acomponent. Optionally possible is both a single-step/multi-step, as wellas an incremental simulation, possibly combined with an evaluationand/or an optimization module. This system is characterized as follows:

Parametric creation of the part tools: From the complete tool surfaces(component+addendum+binder ring), the utilized tools, e.g., the die(complete tool surfaces), the punch (tool surfaces without binder ringand without die radius), and the binder (binder surface cut-out alongthe punch opening line) can be created. An offsetting of the tools, ifso required, is automatically carried out. For the creation of thepunch, if so required, in the wall zone automatically modified sectionalprofiles are utilized (e.g., with a steeper wall angle), in order toproduce the necessary drawing gap. Simultaneously, also the processhistory required for the simulation, i.e., the travel paths of thetools, can be generated automatically. A changing of the addendumtherefore automatically entails the corresponding change of the parttools and of their travel paths.

Parametric creation of the course of the draw beads: Draw beads (beadsattached in the binder zone for controlling the sheet metal draw-in) areautomatically generated on the binder surface at a predefined constantor variable distance from the punch opening line or from anothercharacteristic line of the addendum. A change of this line thenautomatically entails a change of the draw beads.

Parametric creation of the drawn-in sheet metal outline at the end ofthe forming for the inverse simulation: For the inverse simulation, inthe case of which one predefines the geometry at the end of the formingprocess, the drawn-in outline of the sheet metal is also generatedautomatically on the binder surface at a predefined constant or variabledistance from the punch opening line or from another characteristic lineof the addendum. A changing of this line then automatically entails achange of the drawn-in sheet metal outline.

Parametric creation of the blank outline: The blank outline can begenerated in analogy to the draw bead courses described above. Anadditional variant is described in the following: For an as minimal aspossible consumption of material, the blank should be selected as smallas possible. However, the sheet metal outline during the forming ingeneral should not run into the addendum over the punch opening line,i.e., at the end of the drawing process a small flange should remain inthe binder zone. For this reason, the following procedure is chosenhere: First, the drawn-in sheet metal outline for an inverse single-stepsimulation is created as described above. Thereupon the inversesingle-step simulation is carried out. The result of this simulation isthe required blank outline, which is necessary, in order to obtain thepredefined drawn-in sheet metal outline. This procedure is carried outat the beginning of an incremental simulation, in order to find afavourable blank outline for the currently investigated geometryalternative. This procedure makes sense, because the inverse single-stepsimulation requires significantly less calculation time than anincremental simulation. The procedure can be transferred in analogy tothe internal boundaries in case of perforated blanks. In order to savethe tool costs for the trimming tool of the blank, usually a simple,polygonal line blank is preferred, e.g., a rectangular one. If sorequired, the blank outline obtained from the inverse single-stepsimulation is bordered with a rectangle of minimum length and width,whereby the orientation of the rectangle in the horizontal plane ischanged until a rectangle of minimum surface area has been found.Instead of the blank outline obtained from the single-step simulation,this rectangle is now utilized as blank outline for the incrementalsimulation. For other simple polygonal outlines, the procedure isanalogue.

Therefore, every parametric change of the tool surfaces automaticallyresults in a changing of the part tools derived from it, of their travelpaths, of the draw bead course, of the blank outline, etc., so that thesimulation can be restarted again without any manual intervention. Ascompared to the prior art, the effort for the preparation of alternativesimulations, whether manual or carried out automatically within anoptimization loop, can be significantly reduced: When changing theparameters of the tool geometry, immediately and fully automatically anew tool geometry and an appertaining consistent geometry and processmodel for the simulation are created.

If desired, it is possible to use the geometrical information and datarelated to the tool (die, binder, punch) and the sheet metal part,handled and generated by the herein described invention, as input datafor tooling. In this way it is possible to avoid additional processingby a CAD-System, which results in a further optimized process.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the invention will be apparent withreference to the following description and drawings, wherein:

FIG. 1 shows the essential zones of a forming tool;

FIG. 2 illustrates a component;

FIG. 3 shows a course of straight sectional profiles;

FIG. 4 illustrates a course of curved sectional profiles;

FIG. 5 shows a design method of initial directions;

FIG. 6 shows a first addendum with a discontinuous course;

FIG. 7 illustrates a second addendum with a continuous course;

FIG. 8 shows a diagram with the essential optimization steps;

FIG. 9 shows a parameterized sectional profile;

FIG. 10 illustrates a component with an addendum zone;

FIG. 11 shows the component in accordance with FIG. 10 with sectionalprofiles;

FIG. 12 illustrates a component with optimized sectional profiles; and,

FIG. 13 illustrates the interpolation between sectional profiles.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates essential elements of a forming tool 1. Identifiableare a component 2, a component edge 3, an addendum 4, a punch openingline 5 and a binder surface 6.

FIG. 2 shows a component 2 with an irregular component edge 3. Theirregularities in the course of the edge of the component 3 are filledin with fill surfaces 7 and smoothed. Fill surfaces have to mergeC1-continuous (values of the first differentiation identical on bothsides) into the geometry of the component 2. Such surfaces 7 can, forexample, be generated through geometrical approximations underC1-boundary condition on the edge of the component 3, or through afinite element shell solution with C1-boundary condition. The fillsurfaces 7 resulting in this manner are smoothed and continuous andcomplement the component 2 in an optimum manner. In the zone of a fillsurface 7, alternatively an edge 8 of the fill surface 7 is decisive forthe course of the sectional profiles.

FIG. 3 illustrates the situation, as it is known through prior art. Tobe seen is a plan view (in direction of the z-axis) of a section of acomponent 2 with a component edge 3 with a concave course. Straightsectional profiles 10, as they are known through prior art, are arrangedvertically to the edge of the component 3. On the basis of thisarrangement, they manifest overlaps.

FIG. 4 shows a section from the component 2 in accordance with FIG. 3.Identifiable are an addendum 4 and sectional profiles 10. The sectionalprofiles here have been created by means of the method in accordancewith the invention. To be identified is the fact, that in the plan viewthey do not have a straight course, but are curved. In particular, theyhere do not manifest any overlaps. Preferably, they are arranged suchthat they correspond to the natural course of geometrical details of thecomponent. For example, they follow their extended course in theaddendum. With this, the actual edge of the component plays asubordinate role.

FIG. 5 schematically illustrates how the horizontal initial direction ofa sectional profile 10 is generated. This direction is particularlyadvantageously determined by means of the determination of the minimumgeometry change. Identifiable are a component 2, a component edge 3(resp., the edge of a fill surface), and a component edge boundary zone22, which is edged by the edge of the component 3 and an inner limitingline 23. In order to determine the initial direction of a sectionalprofile in a point 25 on the edge of the component 3, resp., if sorequired on the edge of fill surfaces (not illustrated in more detail),a sectional curve 26 between a vertical (parallel to the z-axis) plane24 also running through the point 25 is formed. The deviation of thissectional curve 26 from a straight line 27, represented by a hatchedarea 28, serves as a measure for the geometry change. The surface 24 isnow varied so long by revolving around a vertical axis 30 (illustratedby an arrow 29) running through the point 25, until the geometry changefulfils a certain measure. As a rule, this is a minimum. The initialdirection of a sectional profile in a horizontal plane (x/y-plane),which results from the plane 24, is schematically made clearer by anarrow 31. Another possibility consists of using the curvature in theedge zone of the component 22 as a measure. When using the curvature asa measure for the geometry change, the direction of the correspondingsectional profile is advantageously placed in the direction of thesmaller principal direction of a curvature tensor projected into ahorizontal plane.

FIG. 6 shows the typical course of characteristic lines 11 in anaddendum 4 of a shape for a component 2. The course of thecharacteristic lines 11 on the basis of great differences in height andtangential jumps is disadvantageously irregular.

FIG. 7 illustrates a smoothed course of the characteristic lines 11 inaccordance with FIG. 6. The addendum 4 of the shape for a component 2 asa result manifests a significantly more advantageous design. Therefore,in production much better results are achieved.

FIG. 8 schematically illustrates the essential steps, which arenecessary for the automatic generation of addendums. The addendum isoptimized by means of a so-called optimizer and a quality criterion.

FIG. 9 in a generalized manner shows a parameterized cross section of asectional profile 10 as a representative for a single type of geometry.The sectional profile 10 is parameterized by means of forming technologyscalar values (profile parameters), such as, for example, componentrun-off length, component run-off radius, flange length, flange angle,draw bar height, draw bar width, draw bar radius, step height, stepradius, wall angle, die radius, etc. The sectional profile 10 based onthese profile parameters is built up from basic elements, for examplecircular arcs, splines and line segments, preferably in an automatedmanner. One or more parametric values may be close to or zero ifnecessary. Corresponding points are connected to obtain addendumsurfaces.

FIG. 10 illustrates a geometrical detail 13 and its effect on anaddendum 4. The horizontal directions of the sectional profiles as arule determine how the geometrical detail 13 of the component 2(feature), which extends to the edge of the component, has an effect onthe addendum 4. It is therefore advantageous that such geometricaldetails 13 in the component geometry and their branches 14 in theaddendum 4 essentially have the same direction (which is not the case inthis illustration).

FIG. 11 shows the typical course of sectional profiles 10 which, inaccordance with the procedures known from prior art, are arrangedvertically to a component edge 3. As a result of this, the result shownin FIG. 10 is produced, in the case of which the branches 14 of ageometrical detail 13 continue in an unfavourable direction in theaddendum 4.

FIG. 12 illustrates an arrangement of sectional profiles 10 along theedge of the component 3 in accordance with the invention. The sectionalprofiles are arranged such that the natural course of geometricaldetails 13 in the component 2 is taken into account. The direction ofthe branches 14 as a result of this essentially corresponds to thedirection of the geometrical detail 13 in the zone of the edge of thecomponent 3.

FIG. 13 is showing in a simplified, idealistic manner a part of anaddendum surface 4 and the arrangement of the sectional profiles 10 inaccordance with FIG. 9. The sectional profiles are parameterised suchthat they are adapted to the geometry. The orientation and the distancebetween sectional profiles is not necessarily equal and is adapted tothe course of the geometry. The sectional profiles are built such thatthey are corresponding to each other. Parametric values may be zero orclose to zero such that single elements are not visible. Theintermediate profiles are in this example indirectly interpolated: Firstthe parametric values are interpolated, second the at least one profileis regenerated based on these interpolated values and third the surfaceof the addendum is built up based on these sectional profiles and, ifavailable, intermediate sectional profiles.

What is claimed is:
 1. A method for designing a tool for deep drawing of sheet metal to form a sheet metal component having a predefined component geometry, said tool comprising a die, a binder and a punch, whereby the binder is used to fix the sheet metal in an edge zone of the die, before the sheet metal is pressed in a drawing direction by the punch into the die, said tool comprising at least one addendum zone surrounding the component, said tool is generated by a method comprising: (a) preparing the predefined component geometry; (b) determining a direction of drawing; (c) creating a fill surface for smoothing irregular zones of an edge of the predefined component geometry; (d) generating a binder surface; (e) generating the at least one addendum zone by (i) defining sectional profiles at defined points; (ii) determining sectional profile directions; and (iii) interpolating intermediate profiles using forming technology parameters for creation of the at least one addendum zone (f) interactively adapting characteristic lines and correspondingly adapting the at least one addendum zone; and (g) creating a punch opening line as intersections of the sectional profiles with the binder surface.
 2. The method according to claim 1, wherein the at least one addendum zone is generated by a method comprising the following steps: (a) arranging several sectional profiles along the component edge at a distance from one another and directing away from the component edge; (b) parameterizing the sectional profiles by profile parameters, the profile parameters being scalar values; and (c) laterally interconnecting the sectional profiles by a continuous surface to form the geometry of the addendum zone of the tool, whereby said addendum zone complements the component geometry in the edge zone and runs into the component and the binder with a continuous tangent.
 3. The method according to claim 1, wherein the fill surface is generated by virtual unrolling of a cylinder with a vertical axis along the edge of the component.
 4. The method according to claim 1, wherein a change of the characteristic line in a controlled manner influences several adjacent sectional profiles.
 5. The method according to claim 1, wherein the sectional profile is parameterized by profile parameters out of the group of the following elements: component run-off length, component run-off radius, flange length, flange angle, draw bar height, draw bar width, draw bar radius, step height, step radius, wall angle, die radius.
 6. The method according to claim 5, wherein one or more profile parameter is zero indicating the absence of an element related to said profile parameter.
 7. The method according to claim 1, wherein at least one intermediate profile is arranged between two sectional profiles whereby the addendum is formed by interconnecting the sectional profiles and the intermediate profiles.
 8. The method according to claim 7, wherein the at least one intermediate profile is interpolated indirectly from at least one profile parameter, whereby the profile parameters of the sectional profiles are interpolated, the at least one intermediate profile is interpolated based on the profile parameters of the sectional profiles, and the surface of the addendum is built up by based on the sectional profiles and the intermediate profiles.
 9. The method according to claim 1, wherein characteristic lines are generated by the connection of characteristic points of a sectional profile or as a curve of parameter value in a diagram, whereby the characteristic points describe the principle course of the sectional profile.
 10. The method according to claim 9, wherein the characteristic points are out of the group of the following elements: Summit of a draw-bar; the flank of a step; the control points of a spline, a Bézier- or a Nurbs-Curve.
 11. A method for designing a tool for deep drawing of sheet metal to form a sheet metal component having a predefined component geometry, said tool comprising a die, a binder and a punch, whereby the binder is used to fix the sheet metal in an edge zone of the die, before the sheet metal is pressed in a drawing direction by the punch into the die, said tool comprising at least one addendum zone surrounding the component, said tool is generated by a method comprising: (a) preparing the predefined component geometry; (b) determining a direction of drawing; (c) creating a fill surface for smoothing irregular zones of an edge of the predefined component geometry; (d) generating a binder surface; (e) generating the at least one addendum zone by (i) defining sectional profiles at defined points; (ii) determining sectional profile directions; and (iii) interpolating intermediate profiles using forming technology parameters for creation of the at least one addendum zone (f) interactively adapting characteristic lines and correspondingly adapting the at least one addendum zone; (g) creating a punch opening line as intersections of the sectional profiles with the binder surface; (h) extracting individual tool components from generated geometries; (i) specifying a blank outline; (j) specifying material; (k) specifying thickness of the material; (l) specifying lubrication properties; (m) specifying retaining devices such as draw bead, spacer, binder force; and (n) determining tool movements.
 12. A non-transitory computer readable medium containing a program, said program being configured to make a computer execute the steps of a method according to one of claim
 1. 